Mitral annuloplasty relays on the implant of mitral ring having fixed shape and size. During the classical mitral valve repair procedure, the surgeon sizes the mitral annulus and chooses the mitral ring accordingly. This procedure is done on the arrested heart under cardiopulmonary bypass, which is not a physiologic condition. However, it is only after the weaning off the cardiopulmonary bypass that it is possible to assess the quality of the mitral repair. In other words, the surgeon has to wake up the patient to verify if he succeeded in the mitral repair. If the repair fails, the patient undergoes a second operation. Surgeons and cardiologists express a need in the possibility to adjust the ring after implantation. Having a mitral ring that changes its size after implantation and on a beating heart, could improve the quality of the mitral repair and overcome the annulus miss-sizing problem.
Some solutions have been found to reduce the risk of ineffective mitral annuloplasty.
U.S. Pat. No. 7,713,298 discloses an annuloplasty ring which comprises shape memory members configured to transform said annuloplasty ring from a first configuration having a first size of a ring dimension to other configurations having a size of the ring dimension, which is less than said first size. The shape memory members are responsive to changes in temperature and/or exposure to a magnetic field.
U.S. Pat. No. 5,064,431 discloses an adjustable annuloplasty ring for an orifice, comprising: a flexible fabric tube formed in the shape of a ring, means for dividing the tube into an inner channel and an outer channel which functions as a sewing flange by which the ring may be sutured to tissue surrounding the orifice, at least two drawstrings for adjusting the size and shape of the ring disposed in the inner channel, the drawstrings extending substantially around the circumference of the ring and having ends protruding from openings in the tube, each drawstring being coupled to the tube at least two separate anchor points. The size and shape of the ring may be adjusted by selectively tightening one or more ends of the drawstrings to constrict portions of the ring.
However, the drawback of such mitral rings is that their size can be adjusted only one time after implantation. Another drawback is that the ring, when adjusted, modifies its shape in such a way the ring becomes smaller, therefore the surface of the atrioventricular valve becomes smaller. This downsizing of the annulus could induce valve stenosis and has negative consequence on heart function.
US 2007/0016287 discloses an implantable device for controlling the shape and/or the size of an anatomical structure or lumen. The implantable device has an adjustable ring associated with drawstrings. When the drawstrings are tensioned, the ring is deformed. However, when the drawings are tensioned, a large zone of the ring is deformed. It is not possible to deform a precise part of the ring.
Therefore there are, at the present time, no adequate solutions, whether commercial or in the literature, for a mitral ring having a size which can be changed and adjusted several times after implantation and on a beating heart, on a regular basis.